Image Pick-Up Module And Method For Assembling Such An Image Pick-Up Module

ABSTRACT

An image pick-up module comprises an electronic image sensor, single-piece circuit board electrically bonded to the image sensor, and at least one cable electrically bonded and leading away from the circuit board. The circuit board has at least three sections, first and second section extending in relation to the other and obliquely or crosswise to the image sensor, and third section arranged between first and second section. The image sensor is arranged on the circuit board opposite the third section. In a method for assembling the image pick-up module, the circuit board has the form of a planar board blank comprising at least three sections folded along flexible connecting sections whereby the at least one cable is bonded to the board, and the board folds whereby a third section is located between first and second section, and the image sensor is bonded to the circuit board opposite the third section.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is divisional of pending U.S. patent applicationSer. No. 09/994,178 filed on Nov. 26, 2001, which is a continuation ofInternational Patent Application PCT/EP2000/04792 filed on May 25, 2000,which designates the United States and which claims priority of Germanpatent application 199 24 189 filed on May 27, 1999.

FIELD OF THE INVENTION

The present invention relates to an image pick-up module, especially foran endoscope, comprising an electronic image sensor, a single-piececircuit board which is electrically bonded to the image sensor and towhich is further electrically bonded at least one cable leading awayfrom the circuit board, the circuit board having at least threesections, with a first section and a second section extending in spacedrelation one to the other and obliquely or crosswise to the image sensorand a third section being arranged between the first and the secondsections.

BACKGROUND OF THE INVENTION

The invention further relates to a method for assembling an imagepick-up module, wherein an electronic image sensor is electricallybonded to a single-piece circuit board and the circuit board iselectrically bonded to at least one cable leading away from the circuitboard.

An image pick-up module of the before-mentioned kind is known from U.S.Pat. No. 5,220,198.

Electronic image pick-up modules of this kind find general applicationin the field of video recording. In addition to the use in videocameras, such electronic image pick-up modules have recently beenemployed in maximally miniaturized applications, especially inendoscopes for technical or medical purposes. Such endoscopes, or videoendoscopes, have been disclosed, for example, in U.S. Pat. No. 5,754,313and U.S. Pat. No. 5,166,787.

An image pick-up module comprises, generally, an electronic image sensoror image pick-up, by which light imaged on it is converted into anelectric signal. Such electronic image sensors are generally implementedin CCD or CMOS technology. Further, the image pick-up module comprisesat least one circuit board which accommodates the signal electronics, orat least part of the signal electronics, for the image sensor. Thesignal electronics comprise circuits that are implemented on the circuitboard by electronic components or in the form of printed circuits. Inaddition, the image pick-up module comprises at least one cable, leadingaway from the circuit board, which is connected, at a point remote fromthe image pick-up module, to an electronic control and signal processingsystem for processing the electric signals received from the imagepick-up module to reproduce the image received by the image sensor on animage reproduction unit, such as a display or a monitor.

As a rule, however, the circuit board is bonded not only to a singlecable but to a system of several, partially coaxial, cables which formthe electric signal transmission system between the image pick-up moduleand the electronic control and signal processing system.

It is only due to the miniaturization of the image sensors and theprogress achieved in microtechnology that the use of such image pick-upmodules in endoscopes has become possible. The image pick-up module isarranged in an endoscope in the distal tip of the endoscope shaft, i.e.the tip facing the patient, as is described in the before-mentioned U.S.Pat. No. 5,166,787. The image pick-up module replaces in this case theoptical image transmission system used in “classical” endoscopes, whichconsist of a plurality of lenses arranged in series. Instead oftransmitting the distally received image to the proximal end, i.e. theend remote from the patient, by means of an optical imaging lens system,an image pick-up module converts the optical light signals to electricsignals and transmits them to the proximal end, via at least one cableor, as a rule, a cable system. The use of electronic image pick-upmodules instead of optically transmitting lens systems provides theadvantage, according to the before-mentioned US patent Specification,that the image pick-up module need not be installed rigidly in thedistal tip of the endoscope shaft, but can be mounted movably in thattip so that once the endoscope has been introduced into the cavity to beinspected, the image pick-up module can be pushed out distally from theshaft or can be swung out laterally from the shaft, with the effect thaton the one hand a larger area can be viewed through the movable imagesensor while on the other hand the endoscope shaft is released so thatinstruments can be introduced through the shaft into the cavity, forexample. In addition, a telescope-like extension of the endoscope isalso imaginable.

It is always a requirement with endoscopes that the cross-section of theouter contour of the shaft be as small as possible. Accordingly, inorder to be accommodated in such a shaft, the image pick-up modules usedmust have the smallest possible outer cross-section. The shaft diameterof a video endoscope for medical purposes, for example, is as small as afew millimeters (<10 mm). This means that the dimensions of theminiaturized image pick-up modules should be as small as ever possible(if possible #6 mm). While presently existing image sensors, designed inso-called “case-less” configuration and with flexible connectingfingers, succeed increasingly in meeting these demands, the problem ofmaking the overall structure of the image pick-up modules as small aspossible continues to exist.

The image pick-up module known from U.S. Pat. No. 5,754,313 comprisestwo separate, i.e. not a single-piece, circuit boards for bonding theimage sensor, which two circuit boards accommodate, in customaryfashion, electronic miniature components and serve for bonding the cablesystem. The circuit boards extend in parallel one to the other andsubstantially at a right angle relative to the image pick-up surface ofthe image sensor. Since the signal electronics accommodated on the twocircuit boards cannot function independently, an electric connection,for example in the form of lines, or a connecting circuit board must beadditionally integrated which constitutes a further increase of theassembly effort connected with the image pick-up module. In addition,bonding the cables and the electric components between the boards hasbeen found to present a problem. Further, the cables leading away fromthe circuit board are bonded to the circuit board on an outer surface ofthe latter in the case of this image pick-up module. Given the diameterof the different cables, which in part may be coaxial lines in whichcase they exhibit a corresponding thickness, the described structure ofthe known image pick-up module results in a cross-sectional diametergreater than the cross-sectional diameter defined by the image sensor.

Another problem presenting itself when such image pick-up modules areused in video endoscopes consists in that the one or the several cables,that lead away from the circuit board, may be exposed to tensile strain,especially in the case of flexible video endoscopes or when a deflectionmechanism is provided for moving the image pick-up module, as describedin U.S. Pat. No. 5,166,787, or during installation of the module in theendoscope shaft. Here again, the image pick-up module known from U.S.Pat. No. 5,754,313 has been found to be disadvantageous insofar as thestrain relief device would have to be provided either around the bondingarea of the cables on the two circuit boards, which would furtherdisadvantageously increase the cross-sectional diameter of that knownimage pick-up module, or else would have to be provided at the proximalend of the circuit boards with the result that the length of the imagepick-up module would be additionally increased in an undesirable way,which is a problem especially with flexible endoscopes where the stiffdistal jaw parts should be kept as short as possible.

The image pick-up module known from the before-mentioned U.S. Pat. No.5,220,198, from which the present invention starts, comprises asingle-piece circuit board having three sections forming in this casethe shape of a U; the present invention is, however, not restricted tothat embodiment. The two sections, that are bonded to the image sensor,extend one parallel to other, the image sensor being fastened on thethird section which extends crosswise to the two other sections.Accordingly, the circuit board is open on the side opposite the imagesensor. This image pick-up module also provides the disadvantage that nostrain relief is provided for the cables leading away from the circuitboard. Under tensile strain conditions, there is therefore a risk forthe cables leading away from the circuit board that the one or theseveral cables may be torn off the circuit board under strain.

Now, it is an object of the present invention to improve an imagepick-up module of the before-mentioned kind in such a way that strainrelief is provided, with small constructional effort, for the at leastone cable leading away from the circuit board, without the structuraldimensions of the image pick-up module being increased due to thatstrain relief.

SUMMARY OF THE INVENTION

The invention achieves this object with respect to the before-mentionedimage pick-up module by the fact that the image sensor is arranged onone side of the circuit board opposite the third section.

Instead of bonding the circuit board to the image sensor so that theimage sensor comes to lie on the third section of the circuit board andthe circuit board is open on the side opposite the image sensor, asdescribed for the image pick-up module known from U.S. Pat. No.5,220,198, it is provided by the invention that the circuit board isbonded to the image sensor by arranging the image sensor at the end ofthe circuit board opposite the third section so that the third sectionforms a bottom opposite the image sensor. This arrangement opens up theadvantageous possibility to implement a strain relief device for the atleast one cable leading away from the circuit board. The third sectioncan be used with advantage to provide strain relief for the cablesystem. Another advantage of the configuration of the image pick-upmodule according to the invention consists in that strain relief can beimplemented on the third section without increasing the circumferentialdimensions of the image pick-up module beyond the circumference of theimage sensor, because the third section is arranged between the firstand the second section and does not, therefore, project beyond it. Inaddition, the third section can be used with advantage for the bondingfunction between the first and the second sections.

With respect to the method mentioned at the outset, it is further anobject of the present invention to improve the before-mentioned methodso as to facilitate the preassembly of the signal electronics on thecircuit board and also bonding to the at least one cable.

The invention achieves this object with respect to the before-mentionedmethod by the fact that initially the circuit board has the form of aplanar board blank comprising at least three sections that can be foldedalong flexible connecting sections, that the at least one cable isbonded to the board blank, that thereafter the board blank is folded insuch a way that a third section is located between the first section andthe second section, and that thereafter the image sensor is bonded tothe circuit board at an end of the board opposite the third section.

According to the invention, therefore, once the signal electronics havebeen mounted on the board blank, one initially bonds the at least onecable to the circuit board, having the form of a planar board blank,which is especially easy due to the fact that the different contacts areeasily accessible on the flat-lying circuit board. After the at leastone or the several cables have been bonded to the planar board blank,the board blank is then folded along the flexible connecting sections sothat the first, the second and the third sections of the at least threesections form the desired shape, whereafter the folded structure isbonded to the image sensor. The method according to the invention is,thus, especially well-suited for producing miniaturized image pick-upmodules.

According to a preferred embodiment, the first and the second sectionsextend substantially in parallel one to the other, and the third sectionextends obliquely or crosswise to the first and second sections.

In the case of this embodiment of the circuit board, the board exhibitssubstantially the shape of a U. Since in this case the third sectionextends substantially crosswise to the at least one cable leading awayfrom the circuit board, this embodiment of the circuit board providesthe advantage that the third section is capable of effectively absorbingany tensile forces acting on the at least one cable, in the sense of astrain relief device.

Alternatively, it is, however, likewise preferred if the third sectionhas a substantially V-shaped configuration.

This provides the advantage that the at least one cable leading awayfrom the circuit board can be bonded to the outer surface of theV-shaped third section, which makes bonding of the cable to the circuitboard especially easy. Further, it is also possible with this embodimentto provide strain relief measures on the outer surface of the thirdsection of the circuit board, without increasing the outer circumferenceof the image pick-up module beyond the outer circumference of the imagesensor. Another particular advantage resulting from this arrangement isseen in the especially short overall length that can be achieved for theentire image pick-up module.

It is also possible to provide that two legs of the V-shaped thirdsection extend along a straight-line prolongation of the first and thesecond sections, respectively.

To say it in other words, the circuit board of this embodiment hasgenerally the shape of a V, without any transition being noticeablebetween the first section and the third section, and the second sectionand the third section, respectively.

Alternatively, it is however also preferred if the first and the secondsections extend substantially in parallel one to the other so that inthis case the V-shaped third section, or more exactly its two converginglegs, form an angled transition to the first and second sections,respectively.

According to another preferred embodiment, it is likewise preferred ifthe third section is curved in outward or inward direction. This, too,can be of advantage as regards ease of production and simpleconstructional design of the circuit board.

According to a further preferred embodiment, the at least one cable isbonded to an inner surface of the circuit board.

This provides the advantage that the at least one cable is arranged inthe interior of the folded circuit board so that the cable, especiallyif a coaxial cable is used, or the cables, where a plurality of cablesis used, do not increase the outer dimension of the image pick-upmodule. In the case of the before-mentioned method according to theinvention, the board blank is then folded after the at least one cablehas been bonded, so that the cable comes to lie inside the foldedcircuit board.

Alternatively, it is of advantage, especially when the third section isconfigured in the form of a V, if the at least one cable is bonded to anouter surface of the circuit board, especially to the outside of theV-shaped third section, as has been described before in connection withthe configuration of the third section in the form of a V.

According to a further preferred embodiment of the image pick-up module,the third section comprises at least one passage for the at least onecable leading away from the circuit board.

The passage in the third section of the circuit board, that forms thebottom of the image pick-up module, provides the advantage, especiallyin the embodiment just mentioned, that the cable being bonded to thecircuit board on its inside is guided past the third section withoutprojecting laterally beyond the outer dimension of the circuit boardand, thus, without increasing the outer dimension of the image pick-upmodule. In addition, the at least one passage may, advantageously, serveas strain relief, for example when the cable or the several cables arefixed in their positions in the at least one passage of the thirdsection by corresponding measures, for example by clamps. While thepassage may serve as passage for the entire cable system, there may alsobe provided several passages for the different cables or different cablebundles.

In the case of the method according to the invention, the at least onepassage preferably is produced before the at least one cable isconnected.

In this connection, it is further preferred if the at least one passageis formed as a marginal recess in the third section.

This feature provides the advantage that for bonding the at least onecable to the circuit board, the at least one cable can be positioned onthe circuit board in flat stretched condition so that when the thirdsection is then folded, it can be moved past the cable without anytrouble into its final position, crosswise to the outgoing cable,without the cable forming an obstacle to the folding operation.

It is, however, also preferred if the at least one passage is configuredas a substantially central opening in the third section.

Although this configuration requires that the at least one cable, beforebeing connected, must be threaded through the board blank in its planarspread condition, this feature provides however the advantage that theat least one outgoing cable, or the cable bundle, can be guided off thecircuit board centrally.

According to a further preferred embodiment of the image pick-up module,the interior of the circuit board, defined by the first, second andthird sections, is filled with an electrically non-conductive fillingcompound.

This feature opens up a particularly favorable way of providing strainrelief for the at least one outgoing cable, creating an intimate contactbetween the sections of the circuit board and the at least one outgoingcable, which connection is capable of safely withstanding evenespecially high tensile strains. Another advantage of this feature liesin the fact that strain relief is in this case implemented completelyinside the circuit board so that the image pick-up module is notincreased in dimension. In addition, the filling compound has thefavorable effect of strengthening the overall structure.

The method of the invention thus provides that the interior of thefolded circuit board, defined by the first, second and third sections,is filled up with a curing electrically non-conductive filling compound,whereafter the image sensor is bonded to the circuit board.

This permits strain relief to be implemented by an especially simpleprocedure since a curing filling compound can be introduced into theinterior of the circuit board in its soft or even flowing condition,without any effort.

The filling compound used may be a curing resin, for example atwo-component adhesive. The folded circuit board may be placed for thispurpose in a mold or casing to prevent the filling compound fromescaping before it has cured.

According to another preferred embodiment of the image pick-up module,the circuit board comprises a forth section arranged opposite the thirdsection and accommodating the image sensor on its outer surface.

The forth section, therefore, advantageously serves as a planar supportor carrying plate for the image sensor so that the latter can beconnected with the circuit board in a mechanically safe manner, inaddition to fastening it on the outer surface of the first and secondsections via the bonding arrangement. Further, the forth section can,advantageously, accommodate additional components while being connectedwith the image sensor only mechanically and, normally, not electrically,if desired.

According to the method of the invention, where the circuit board isfolded from a planar board blank, the board blank may also comprise theforth section, flexibly and integrally connected with one or more of thebefore-mentioned three sections, so that the assembly effort is notincreased by that arrangement.

It is further preferred in this connection if the forth sectioncomprises at least one electric component and/or at least one electriccircuit-board conductor.

This arrangement provides the advantage that the forth section alsoprovides the possibility of accommodating parts of the signalelectronics so that there is, generally, more room available for thecircuits and electronic components.

According to a further preferred embodiment, the circuit boardcomprises, in addition to the first section and the second section, oneor two additional sections arranged on a longitudinal side of thecircuit board.

This feature provides the advantage that the signal electronics of thecircuit board can be entirely enclosed on all sides by sort of a casingand can thus be protected from damage. Another advantage of this featureis seen in the fact, in connection with filling the interior of thecircuit board with a curing filling compound, that by enclosing theinterior of the circuit board on all sides, the filling compound can belargely prevented from escaping before curing, even without anyadditional encasing measures.

According to a further preferred embodiment, the circuit board isprovided on its outer surface with recesses for bonding of the imagesensor.

Since, usually, the contact fingers of the image sensor are bonded tothe circuit board on the outer surfaces of the circuit board, thisfeature provides the advantage that the contact fingers can be placed inthe recesses with the result that the outer dimensions are not increasedby the electric bond between the image sensor and the circuit board.

According to a further preferred embodiment, the third section of thecircuit board comprises at least one contact for bonding the cableleading away from the circuit board.

In connection with the embodiment where the circuit board comprises abottom in the form of the third section, the latter can be used withadvantage for bonding further cables or a shielding line for the entirecable, or a multi-core cable, respectively, in which case those cablescan be bonded to the third section in similar strain-relieved fashion bycorresponding measures.

According to another preferred embodiment, the third section of thecircuit board comprises at least one electric circuit-board conductorfor electrically connecting the first section and the second section.

This feature provides the advantage that the third section, in additionto fulfilling a strain-relief function, may serve to electricallyconnect the first and the second sections without any additional linesor connecting circuit boards being required for that purpose.

An especially preferred board blank, from which the circuit board isfolded, is configured in such a way that the first section and thesecond section are flexibly connected via an additional section, but arearranged in spaced relationship at one and the same level, that thefirst section and the second section each serve for bonding at least onecable, and that the third section is flexibly connected to theadditional section on the latter's end face.

A board blank configured in this way makes the preassembly of the signalelectronics and, above all, the connection of a plurality of cablesespecially easy because it is thus possible to bond a cable bundle toeach of the first and the second sections so that the cable bundles arespaced one from the other and will not obstruct each other, and becausethe subsequent folding operation, by which the circuit board is finishedand given its final structure, is also rendered particularly easy,especially when the passages in the third section are formed as marginalrecesses.

Instead of filling the interior of the circuit board, being defined bythe first, second and third sections, with a filling compound, asmentioned before, it may also be provided to fill that interior with acontact body which on the one hand establishes contact with the firstsection and the second section and, on the other hand, embodies aplug-in connector system for the at least one outgoing cable.Preferably, such a plug-in connector implemented within the contact bodyis a microconnector system. Due to the progress achieved inmicrotechnology, it is possible today to produce such microconnectorsystems.

Further advantages are evident from the description below and theappended drawings.

It is understood that the features recited above and those yet to beexplained below can be used not only in the respective combinationindicated, but also in other combinations or in isolation, withoutleaving the context of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in the drawings and areexplained in more detail in the description which follows. In thedrawings:

FIG. 1 shows a perspective view of an image pick-up module according toa first embodiment;

FIG. 2 shows a sectional view taken along line II-II in FIG. 1;

FIG. 3 shows a top view of a board blank from which is folded thecircuit board of the image pick-up module illustrated in FIGS. 1 and 2;

FIG. 4 shows a perspective view of an image pick-up module according toa second embodiment;

FIG. 5 shows a sectional view taken along line V-V in FIG. 4;

FIG. 6 shows a top view of a board blank from which has been folded thecircuit board of the image pick-up module illustrated in FIGS. 4 and 5;

FIG. 7 shows a perspective view of an image pick-up module according toa third embodiment;

FIG. 8 shows a side view of the image pick-up module illustrated in FIG.7;

FIG. 9 shows a sectional view taken along line IX-IX in FIG. 8;

FIG. 10 shows a top view of a board blank from which has been folded thecircuit board of the image pick-up module illustrated in FIGS. 7 to 9;

FIG. 11 shows a perspective view of an image pick-up module according toa forth embodiment;

FIG. 12 shows a top view of a board blank from which has been folded thecircuit board of the image pick-up module illustrated in FIG. 11; and

FIG. 13 shows a longitudinal section through an image pick-up moduleaccording to a fifth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an electronic image pick-up module, indicated generally byreference numeral 10. The image pick-up module 10 is installed, forexample, in the distal tip of an endoscope shaft not shown. Asillustrated in FIG. 1, the image pick-up module 10 is ready for beinginstalled, which means that the image pick-up module 10 will not beenclosed in an additional casing; as will be shown in the descriptionthat follows, there is no need for such an additional enclosure in thecase of that embodiment of the image pick-up module 10 according to theinvention since all sensitive and, possibly, strain-loaded elements aresafely protected.

The image pick-up module 10 comprises an image sensor 12 with an imagepick-up surface 14.

The image sensor 12 is an electric image sensor in CCD or CMOStechnology. Such image sensors are commercially available. Image sensorsof this kind constitute optoelectronic converters, which means thatlight, which is received via the image pick-up surface 14 pixel forpixel, is converted to electric signals by the image sensor 12.

Specifically, the image sensor 12 is a miniaturized image sensor whoseouter edges 16 and 18 each have a length of about 4 mm, to mention oneexample only. In addition, the image sensor 12 is designed without acasing in what is known as TAB technology, with the contacts projectinglaterally from the sensor. The design of the image sensor 12 without acasing further contributes toward realizing a space-saving structure ofthe image pick-up module.

The image pick-up module 10 further comprises a circuit board indicatedgenerally by reference numeral 20. The circuit board 20 is formedentirely in one piece.

The circuit board 20 comprises a first section 22 and a second section24. The first section 22 and the second section 24 extend in spacedrelation to and substantially parallel one to the other, andsubstantially perpendicularly to the image sensor 12 or the imagepick-up surface 14.

Further, the circuit board comprises a third section 26 extendingcrosswise to the first section 22 and crosswise to the second section24, and substantially parallel to the image sensor 12 or the imagepick-up surface 14. The third section 24 connects the first section 22and the second section 24 to form a single piece in this case.

The third section 26 is integrally connected with the first section 22via a first flexible connecting section 28, and with the second section24 via a second flexible connecting section 30. As can be seen in FIG.1, the first section 22 and the second section 24 have a thicknessgreater than the thickness of the third section 26 and the connectingsections 28 and 30.

The circuit board 20 further comprises a forth section 32 which isflexibly and integrally connected with the second section 24, via athird flexible connecting section 34. The forth section 32 extendssubstantially parallel to the third section 26 and is arranged oppositethe latter on the other end of the circuit board 20.

The first section 22, the second section 24 and the third section 26exhibit together the shape of a U.

The circuit board 20, or more specifically the first section 22 and thesecond section 24 of the circuit board 20, accommodate in this casemicroelectronic components, electric circuit-board conductors, printedelectric circuits, and the like, constituting the signal electronics ofthe image sensor 12.

The image sensor 12 is electrically bonded to the circuit board 20, morespecifically to the first section 22 and the second section 24. Theimage sensor 12 is provided to this end with a plurality of contactfingers 36, in the illustrated embodiment with five contact fingers 36and, opposite the latter, additional five contact fingers, which projectto the outside on opposite sides of the image sensor 12. Bonding of theimage sensor 12 to the circuit board 20 is effected on an outer surface38 of the first section 22 or an outer surface 40 of the second section24 of the circuit board 20, opposite the outer surface 38, for whichpurpose corresponding contact areas 42 are provided on the outersurfaces 38 and 40. The contact areas 42 are arranged in recesses in theouter surfaces 38 and 40 so that the contact fingers 36 of the imagesensor 12 come to lie in these recesses and do not, consequently,project laterally to the outside.

Further, at least one electric cable 44 leading away from the circuitboard 20 is bonded to the circuit board 20; in the illustratedembodiment a cable system comprising a plurality of cables 44 leads awayfrom the circuit board 20. The cables 44 lead to a remote electronicsignal-processing and/or control system, not shown, for the imagepick-up module 10, and may be bundled in a jacket, for example a plasticjacket.

The electric connection of the cables 44 is realized on the innersurfaces 46 and 48 of the second section 24 or the first section 22,respectively, of the circuit board 20, for which purpose the innersurfaces 46 and 48 are provided with corresponding contact areas 50which, just as the contact areas 42 on the outer surfaces 38 and 40, arearranged in corresponding recesses.

Since the third section 26 is arranged opposite the image sensor 12, asmentioned before, the third section 26 forms a bottom which permits astrain relief device to be implemented without any additionalspace-consuming measures that would increase the outer dimension of theimage pick-up module 10.

In the first place, a passage 52 is provided in the third section 26 inthe form of a substantially central opening through which the cables 44are passed. Initial strain relief is achieved by passing the cables 44through the passage 52 due to the fact that relative displacementbetween the cables in the passage 52 in lengthwise direction is hinderedby the frictional grip of the different cables 44 on the edge of thepassage 52 and between the different cables 44.

In the case of the image pick-up module 10, a strain relief device,effective under particularly high strain conditions, is achieved byfilling the interior of the circuit board 20, which is defined by thefirst section 22, the second section 24 and the third section 26 and inwhich the ends of the cables 44 are bonded to the circuit board 20, witha non-conductive filling compound that achieves an especially intimateconnection between the cables 44 and the circuit board 20 due to thefact that the filling compound fills up all, or almost all, of theremaining cavities inside the circuit board. The filling compound mayconsist, for example, of a cured resin, for example a two-componentadhesive which is not conductive electrically.

As can further be seen in FIG. 1, the image sensor 12 is arranged on theforth section 32 of the circuit board 20 so that the forth section 32serves as an additional mount for the image sensor 12 on the circuitboard 20.

FIG. 3 shows a board blank 54 from which the circuit board 20 of theimage pick-up module 10 illustrated in FIGS. 1 and 2 has been folded.

A method for assembling the image pick-up unit 10 operates as follows.Starting out from the planar board blank 54, one initially applies themicroelectronic components, conductors and the like, on the firstsection 22 and the second section 24, i.e. the surfaces that laterbecome the inner surfaces 48 and 46 (the surface shown in the top viewof FIG. 3). With the board blank 54 still in the unfolded, i.e. itsplanar condition the cables 44 are then bonded to the first section 22and the second section 24, in the contact areas 50. Before, thecorresponding cable ends of the cables 44 were passed through thepassage 52 provided in the third section 26 of the circuit board 20 inthe form of the substantially central opening, produced in the thirdsection 26 of the board blank 54 prior to the bonding process.

Once all cables 44 have been bonded to the board blank 54, the sections22, 24, 26 and 32 are then folded to obtain the shape of the circuitboard 20 illustrated in FIG. 1. Thereafter, the interior of the circuitboard 20 is filled with a curing filling compound which, in the curedcondition, strengthens the entire structure of the image pick-up module10 and ensures additional strain relief for the cables 44. Finally, theimage sensor 12 is bonded to the circuit board 20.

The third section 26 may likewise comprise electric circuit-boardconductors for electrically connecting the first section 22 and thesecond section 24 of the circuit board 20.

FIGS. 4 and 5 show another embodiment of an image pick-up module 60. Inthe description that follows, reference will be made mainly to thedifferences from the embodiment previously described, while features notmentioned in that description are identical or similar to correspondingfeatures of the image pick-up module 10.

In this embodiment, the image sensor 12 is bonded to a circuit board 62comprising a first section 64, a second section 66 and a third section68 that together form the shape of a U. The circuit board 62 is likewiseformed entirely as a single piece. The third section 68 is arrangedopposite the image sensor 12. A forth section 70, corresponding to theforth section 32 of the circuit board 20 in FIGS. 1 to 3, serves againas mechanical mount and/or support for the image sensor 12.

In addition to the before-mentioned sections, the circuit board 62comprises, however, a fifth section 72 and a sixth section 74 whichconnect the first section 64 and the second section 66 in the form oflateral walls.

The image sensor 12 is bonded in this case to the sections 72 and 74,while the cables 64 are bonded to the first section 64 and the secondsection 66.

Consequently, the circuit board 62 forms a casing with walls on allsides, in which the signal electronics and the bonds of the cables 44are safely protected. The interior space of this embodiment may likewisebe filled with a cured filling compound in order to provide foradditional strain relief of the cables 44.

The third section 68 comprises at least one passage for the cables 44,in the embodiment shown two passages 76 and 78, which are, however, notconfigured as a central opening but rather as marginal recesses providedin the edge of the third section 68, as can be seen in FIG. 6. Duringassembly of the image pick-up module 60, this provides the advantagethat the cables 44 need not be threaded through an opening before beingbonded to the first section 64 and the second section 66.

A planar board blank 80, from which the circuit board 62 is folded, isillustrated in FIG. 6.

In this case, the first section 64 and the second section 66 of theboard blank 80 are arranged one parallel to the other and at the samelevel, and are connected one with the other in spaced relationship bythe further section 74. The third section 68 is connected with thefurther section 74 on its end face.

In the case of this board blank 80, bonding of the cables 44 to thefirst section 64 and to the second section 66 is particularly easybecause the cables 44 can be arranged in two parallel lines, with theirlongitudinal extension lying in the plane of the board blank 80, andneed not be passed through an opening before. Thus, the cables 44 can beplaced on the working support in fully stretched condition, i.e. withoutany bend. After completion of the bonding process, the differentsections 64 to 74 can then be folded along flexible connecting sections82 to 90 so as to obtain the structure of the circuit board 62illustrated in FIG. 4, during which operation the third section 68, withthe passages 76 and 78, can be folded easily without being obstructed bythe two cable bundles 44.

It is further provided in this embodiment that the forth section 70 ofthe circuit board 62 is likewise equipped with contacts 92.

FIGS. 7 to 9 show an image pick-up module 100 according to anotherembodiment of the invention that differs from the previously describedembodiments by certain individual features of a circuit board 102.

The circuit board 102 comprises a first section 104, a second section106, a third section 108 and a forth section 110, all of them beingconnected to form a single piece, with the first section 104, the secondsection 106 and the third section 108 forming the shape of a U. Incontrast to the two previous embodiments, there is however no directconnection between the third section 108 and the second section 106. Acorresponding planar board blank 112, from which the circuit board 102is folded to obtain the structure illustrated in FIGS. 7 and 8, isillustrated in FIG. 10.

The third section 108 of the circuit board 102 offers additional bondingpossibilities for part of the cables 44, for which purpose additionalopenings 114 are provided in the third section 108. A passage 116 forthe remaining cables 44 is again provided in the third section 108 sothat that part of the cables 44 can be bonded to the inner surfaces ofthe sections 104 and 106 of the circuit board 102.

Finally, a forth embodiment, being very similar to the embodimentillustrated in FIGS. 1 to 3 and constituting an extension of thatembodiment, is illustrated in FIGS. 11 and 12. According to thisembodiment, an image pick-up module 120 comprises a single-piece circuitboard 122 having, in addition to the first four sections 22, 24, 26, 32shown in FIG. 1, a fifth section 124 and a sixth section 128, which areintegrally formed with the first section 22, as shown in FIG. 12, andwhich form a lateral termination of the circuit board 122. Acorresponding planar board blank 130, from which the circuit board 122is folded, is illustrated in FIG. 12.

FIG. 13 shows yet another embodiment of an image pick-up module 140which differs from the embodiments previously discussed especially bythe following features:

The image pick-up module 140 comprises a circuit board 148 having, asbefore, a first section 150 and a second section 152 as well as a thirdsection 154.

In contrast to the previously described third sections, the thirdsection 154 exhibits, however, the shape of a V. The third section 154has a first leg 153 and a second leg 155 converging toward the endopposite the image sensor 12.

The first leg 153 extends obliquely to the second section 152, or formsan angle with the latter, while the second leg 155 forms an angle withthe first section 150. Alternatively, it may however be provided thatthe first leg 153 forms a straight-line prolongation of the secondsection 152, which means that in this case the second section 152 alsoextends obliquely to the image sensor 12, and similarly the second leg155 of the third section 154 may form a straight-line prolongation ofthe first section 150. In this case, the entire circuit board 148 wouldthen exhibit the shape of a V.

As can be seen in FIG. 13, the at least one cable 44 is bonded to thecircuit board 148 on an outer surface thereof, more specifically on anouter surface of the V-shaped third section 154. As illustrated in FIG.13, bonding the at least one cable 44 to the outer surface of theV-shaped third section 154 does not in this case increase thecircumference of the image pick-up module 140 beyond the outercircumference of the image sensor 12. However, it may also be providedto bond the at least one cable 44 to the circuit board 148 on an innersurface of the latter, as has been described in connection with thepreviously discussed embodiments.

In addition, a strain relief device (not shown) may be provided in thearea of the outer surface of the third section 154 of the circuit board148, for example in the form of clamps or the like. Another strainrelief measure may consist in filling the interior of a casing 160, inwhich the image pick-up module 140 is arranged, with a curing fillingcompound.

The circuit board 148 likewise comprises a forth section 156 carrying,or intended to carry, further electric or electronic components. Contactfingers 158, through which the image sensor 12 is bonded to the outersurface of the circuit board 148, are likewise shown in FIG. 13. A glasscover 146 closes off the distal end of the casing 160 in front of theimage sensor 12.

The overall length of the image pick-up module 140 is shorter than thatof the previously discussed embodiments. The previous embodiments showthat a great number of modifications is possible within the scope of thepresent invention, with all such modifications offering the advantage ofproviding strain relief for the cables leading away from the circuitboard, without increasing the outer dimensions of the respective imagepick-up module; this is achieved by the third section at the bottom ofthe circuit board.

1. An image pick-up module, especially for an endoscope, comprising: anelectronic image sensor; a single-piece circuit board which iselectrically bonded to said image sensor, said circuit board having atleast three sections, with a first section and a second sectionextending in spaced relation one to the other and obliquely or crosswiseto said image sensor and a third section being arranged between thefirst and the second sections; at least one cable electrically bonded tosaid circuit board and leading away from said circuit board; whereinsaid image sensor is arranged on one end of said circuit board oppositesaid third section.
 2. The image pick-up module of claim 1, wherein saidfirst and second sections extend substantially in parallel one to theother, and said third section extends obliquely or crosswise to saidfirst and second sections.
 3. The image pick-up module of claim 1,wherein said third section is curved.
 4. The image pick-up module ofclaim 1, wherein said at least one cable is bonded to an inner surfaceof the circuit board.
 5. The image pick-up module of claim 1, whereinsaid at least one cable is bonded to an outer surface of said circuitboard.
 6. The image pick-up module of claim 1, wherein said thirdsection comprises at least one passage for said at least one cableleading away from said circuit board.
 7. The image pick-up module ofclaim 6, wherein said at least one passage is configured as a marginalrecess in said third section.
 8. The image pick-up module of claim 1,wherein said third section comprises at least one passage for said atleast one cable leading away from said circuit board, wherein said atleast one passage is configured as a substantially central opening insaid third section.
 9. The image pick-up module of claim 1, wherein aninterior of said circuit board, defined by said first, second and thirdsections, is filled with an electrically non-conductive feelingcompound.
 10. The image pick-up module of claim 1, wherein said circuitboard comprises a forth section arranged opposite said third section andaccommodating said image sensor on its outer surface.
 11. The imagepick-up module of claim 9, wherein said forth section comprises at leastone of an electric component and at least one electric circuit-boardconductor.
 12. The image pick-up module of claim 1, wherein said circuitboard comprises, in addition to said first section and said secondsection, at least one additional section arranged on one longitudinalside of said circuit board.
 13. The image pick-up module of claim 1,wherein said circuit board is provided on its outer surface withrecesses for bonding of said image sensor.
 14. The image pick-up moduleof claim 1, wherein said third section of said circuit board comprisesat least one contact for bonding said cable leading away from saidcircuit board.
 15. The image pick-up module of claim 1, wherein saidthird section of said circuit board comprises at least one electriccircuit-board conductor for electrically connecting said first sectionand said second section.
 16. The image pick-up module of claim 1,wherein said circuit board is folded from a planar board blankcomprising at least said integrally formed first, second and thirdsections.
 17. The image pick-up module of claim 16, wherein said firstsection and said second section of said board blank are flexiblyconnected via an additional section, but are arranged in spacedrelationship at one and the same level, wherein said first section andsaid second section each serve for bonding said at least one cable, andwherein said third section is flexibly connected to said additionalsection on an end face of said additional section.
 18. A method forassembling an image pick-up module, comprising the steps of:electrically bonding an electronic image sensor to a single-piececircuit board; electrically bonding at least one cable leading away fromsaid circuit board to said circuit board; wherein said circuit boardinitially has the form of a planar board blank comprising at least threesections that can be folded along flexible connecting sections, whereinsaid at least one cable is bonded to said board blank, wherein saidboard blank is then folded in such a way that a third section is locatedbetween a first section and a second section, and wherein said imagesensor is bonded to said circuit board at an end of said board oppositesaid third section.
 19. The method of claim 18, wherein after bonding ofsaid at least one cable an interior of said circuit board is filled upwith a curing electrically non-conductive filling compound.